Field
Advancements in wireless roaming in wireless mesh networks are needed to provide improvements in cost, profitability, performance, efficiency, and utility of use.
Related Art
Unless expressly identified as being publicly or well known, mention herein of techniques and concepts, including for context, definitions, or comparison purposes, should not be construed as an admission that such techniques and concepts are previously publicly known or otherwise part of the prior art. All references cited herein (if any), including patents, patent applications, and publications, are hereby incorporated by reference in their entireties, whether specifically incorporated or not, for all purposes.
A generic wireless infrastructure to support roaming of mobile units, each of which is responsible for switching traffic between clients connected to the mobile units and those connected to the fixed backbone network, generally is subjected to one or more of the following problems:                1. Unpredictable handoff patterns: mobile units can roam from any access-point (AP) to another, purely based on instantaneous signal strength values, resulting in unpredictable changes in RF conditions which leads to unpredictable changes in data rates.        2. Unnecessary handoffs: Each handoff from one access-point to another carries with it a penalty both in terms of additional computation because of tearing down and establishment of links and in re routing of traffic through the new access-point and any accompanying losses. A traditional wireless infrastructure does nothing to minimize these handoffs.        3. Ping pong effect: A phenomenon related to the above mentioned problem of unnecessary handoffs often occurs when a mobile unit decides to roam to a particular access-point purely based upon the signal strength seen from it, only to find itself roaming back to its previous attachment in a very short span of time, due to bad or unstable RF conditions. This typically happens when the mobile unit decides to roam either too early or too late to the next access-point.        4. Attachment in unstable RF zones: overlapping odd numbered Fresnel zones and other RF phenomena can result in unstable RF zones wherein, even when the signal strengths are very high, data traffic may suffer from packet losses and fluctuations in throughput. For example, the region immediately around the antenna of any wireless unit is an unstable region with unpredictable RF characteristics, which are bound to change drastically as soon as the mobile unit crosses the antenna. If a mobile unit decides to roam to an access-point in such a region, its traffic will automatically suffer.        
Thus, improvements in wireless infrastructure to better support the roaming of mobile units, and minimize or avoid the above problems, are desired.